Hazard Matrix: How to Use a Risk Assessment Matrix in Safety

What is a Hazard Matrix?

A hazard matrix also called a risk assessment matrix, risk matrix, or composite risk assessment is a visual tool used to evaluate and prioritise risks based on two factors: the likelihood (probability) that a hazard will result in harm, and the severity (consequence) of that harm if it occurs.

The matrix produces a combined risk rating that helps safety professionals decide which hazards to address first, whether existing controls are adequate, and whether a task is safe to proceed. It is used inside JHA, AHA, JSA, and standalone risk assessment documents.

How to Read a Risk Assessment Matrix (Likelihood × Severity)

The standard risk matrix works as follows:

• Likelihood (Probability): How likely is it that this hazard will actually cause harm? Rated from Improbable (almost never) to Frequent (regularly expected).
• Severity (Consequence): If the hazard results in harm, how bad will it be? Rated from Negligible (minor first aid) to Catastrophic (death or permanent disability).
• Risk Rating: Likelihood × Severity = Combined risk level (Critical, Serious, Moderate, or Low).

USACE EM 385-1-1 Risk Assessment Code (RAC) Matrix

RAC Scoring: Residual vs Initial Risk

Every JHA and AHA should include two RAC scores for each hazard:

• Initial RAC (Before Controls): The risk level if no controls were in place. This shows the inherent danger of the hazard.
• Residual RAC (After Controls): The risk level once all documented control measures are applied. This is the risk your workers will actually face.
• Target: All residual RAC scores should be 3 (Moderate) or 4 (Low) before work proceeds. A residual RAC of 1 (Critical) means your controls are insufficient and work should not start.

Hazard Matrix Example for Construction Tasks

OSHA vs EM 385-1-1 Risk Rating Systems

• OSHA does not mandate a specific risk matrix format. Companies may use High/Medium/Low, numerical scales, colour-coded systems, or RAC codes.
• EM 385-1-1 requires the specific RAC matrix shown above (Probability A–E × Severity I–IV). RAC 1 = Critical, RAC 2 = Serious, RAC 3 = Moderate, RAC 4 = Low.
• ISO 45001 recommends a risk matrix approach but does not prescribe a specific format companies define their own scales.
• AS/NZS 4360 (Australia/NZ) uses a 5×5 matrix with Consequence ratings from Insignificant to Catastrophic and Likelihood from Rare to Almost Certain.

Using Hazard Matrix Inside a JHA or AHA Document

In QuickJHA-generated documents, the RAC matrix is applied automatically. For each job step and associated hazard, the AI assigns an initial RAC score based on the hazard type and task context, then reassigns a residual RAC after documenting appropriate control measures. This ensures every document is internally consistent and demonstrates that controls are proportionate to the hazard level.

See how RAC scoring works in a live JHA at quickjha.com